MAX811REUS-T - Maxim Integrated

19-0411; Rev 6; 5/18

General Description

The MAX811/MAX812 are low-power microprocessor

(μP) supervisory circuits used to monitor power supplies

in μP and digital systems. They provide excellent circuit

reliability and low cost by eliminating external compo-

nents and adjustments when used with 5Vpowered or

3V-powered circuits. The MAX811/MAX812 also provide

a debounced manual reset input.

These devices perform a single function: They assert a

reset signal whenever the VCC supply voltage falls below

a preset threshold, keeping it asserted for at least 140ms

after VCC has risen above the reset threshold. The only

difference between the two devices is that the MAX811

has an active-low RESET output (which is guaranteed

to be in the correct state for VCC down to 1V), while the

MAX812 has an active-high RESET output. The reset

comparator is designed to ignore fast transients on VCC.

Reset thresholds are available for operation with a variety

of supply voltages.

Low supply current makes the MAX811/MAX812 ideal for

use in portable equipment. The devices come in a 4-pin

SOT143 package.

Applications

● Computers

● Controllers

● Intelligent Instruments

● Critical μP and μC Power Monitoring

● Portable/Battery-Powered Equipment

Benets and Features

● Integrated Voltage Monitor Increases System

Robustness with Added Manual Reset

• Precision Monitoring of 3V, 3.3V, and 5V

Power-Supply Voltages

• 140ms Min Power-On-Reset Pulse Width

• RESET Output (MAX811), RESET Output

(MAX812)

• Guaranteed Over Temperature

• Guaranteed RESET Valid to VCC = 1V (MAX811)

• Power-Supply Transient Immunity

● Saves Board Space

• No External Components

• 4-Pin SOT143 Package

● Low Power Consumption Simplifies Power-Supply

Requirements

• 6μA Supply Current

*This part offers a choice of five different reset threshold voltages.

Select the letter corresponding to the desired nominal reset

threshold voltage, and insert it into the blank to complete the

part number.

Devices are available in both leaded and lead(Pb)-free packaging.

Specify lead-free by replacing “-T” with “+T” when ordering.

RESET THRESHOLD

SUFFIX VOLTAGE (V)

4.63

4.38

3.08

2.93

2.63

PART* TEMP RANGE PIN-PACKAGE

MAX811_EUS-T -40°C to +85°C 4 SOT143

MAX812_EUS-T -40°C to +85°C 4 SOT143

MAX811

MAX812

VCC

RESET

(RESET)

RESET

INPUT

GND

VCC

GND

µP

( ) ARE FOR MAX812

PUSHBUTTON

SWITCH

VCC

MR(RESET) RESET

GND

MAX811

MAX812

SOT143

TOP VIEW

( ) ARE FOR MAX812

NOTE: SEE PACKAGE INFORMATION FOR MARKING INFORMATION.

MAX811/MAX812 4-Pin μP Voltage Monitors

with Manual Reset Input

Typical Operating Circuit Pin Conguration

Ordering Information

Click here for production status of specic part numbers.

Terminal Voltage (with respect to GND)

VCC .....................................................................-0.3V to 6.0V

All Other Inputs ..................................... -0.3V to (VCC + 0.3V)

Input Current, VCC, MR ......................................................20mA

Output Current, RESET or RESET ....................................20mA

Continuous Power Dissipation (TA = +70°C)

SOT143 (derate 4mW/°C above +70°C) .....................320mW

Operating Temperature Range ........................... -40°C to +85°C

Junction Temperature ......................................................+150°C

Storage Temperature Range ............................ -65°C to +160°C

Lead Temperature (soldering, 10sec) .............................+300°C

(VCC = 5V for L/M versions, VCC = 3.3V for T/S versions, VCC = 3V for R version, TA = -40°C to +85°C, unless otherwise noted.

Typical values are at TA = +25°C.) (Note 1)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Operating Voltage Range VCC

TA = 0°C to +70°C 1.0 5.5 V

TA = -40°C to +85°C 1.2

Supply Current ICC

MAX81_L/M, VCC = 5.5V, IOUT = 0 615 µA

MAX81_R/S/T, VCC = 3.6V, IOUT = 0 2.7 10

Reset Threshold VTH

MAX81_L TA = +25°C 4.54 4.63 4.72

TA = -40°C to +85°C 4.50 4.75

MAX81_M TA = +25°C 4.30 4.38 4.46

TA = -40°C to +85°C 4.25 4.50

MAX81_T TA = +25°C 3.03 3.08 3.14

TA = -40°C to +85°C 3.00 3.15

MAX81_S TA = +25°C 2.88 2.93 2.98

TA = -40°C to +85°C 2.85 3.00

MAX81_R TA = +25°C 2.58 2.63 2.68

TA = -40°C to +85°C 2.55 2.70

Reset Threshold Tempco 30 ppm/°C

VCC to Reset Delay (Note 2) VOD = 125mV, MAX81_L/M 40 µs

VOD = 125mV, MAX81_R/S/T 20

Reset Active Timeout Period tRP VCC = VTH(MAX) 140 560 ms

MR Minimum Pulse Width tMR 10 µs

MR Glitch Immunity (Note 3) 100 ns

MR to Reset Propagation

Delay (Note 2) tMD 0.5 µs

MR Input Threshold

VIH VCC > VTH(MAX), MAX81_L/M 2.3

VIL 0.8

VIH VCC > VTH(MAX), MAX81_R/S/T 0.7 x VCC

VIL 0.25 x VCC

MR Pull-Up Resistance 10 20 30 kΩ

RESET Output Voltage

(MAX812)

VOH ISOURCE = 150µA, 1.8V < VCC < VTH(MIN) 0.8 x VCC

VOL

MAX812R/S/T only, ISINK = 1.2mA,

VCC = VTH(MAX) 0.3

MAX812L/M only, ISINK = 3.2mA,

VCC = VTH(MAX) 0.4

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MAX811/MAX812 4-Pin μP Voltage Monitors

with Manual Reset Input

Absolute Maximum Ratings

Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these

or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect

device reliability.

Electrical Characteristics

(VCC = 5V for L/M versions, VCC = 3.3V for T/S versions, VCC = 3V for R version, TA = -40°C to +85°C, unless otherwise noted.

Typical values are at TA = +25°C.) (Note 1)

Note 1:

Production testing done at TA = +25°C, over temperature limits guaranteed by design using six sigma design limits.

Note 2:

RESET output for MAX811, RESET output for MAX812.

Note 3:

“Glitches” of 100ns or less typically will not generate a reset pulse.

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

RESET Output Voltage

(MAX811)

VOL

MAX811R/S/T only, ISINK = 1.2mA,

VCC = VTH(MIN) 0.3

MAX811L/M only, ISINK = 3.2mA,

VCC = VTH(MIN) 0.4

ISINK = 50µA, VCC > 1.0V 0.3

VOH

MAX811R/S/T only, ISOURCE = 500µA,

VCC > VTH(MAX) 0.8 x VCC

MAX811L/M only, ISOURCE = 800µA,

VCC > VTH(MAX) VCC - 1.5

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MAX811/MAX812 4-Pin μP Voltage Monitors

with Manual Reset Input

Electrical Characteristics (continued)

(TA = +25°C, unless otherwise noted.)

SUPPLY CURRENT vs. TEMPERATURE

(MAX81_L/M)

MAX811/12-TOC2

TEMPERATURE (°C)

SUPPLY CURRENT (µA)

-40 85

10-15 6035

VCC = 5.5V

VCC = 3V

VCC = 1V

190

POWER-UP RESET TIMEOUT

vs. TEMPERATURE

230

MAX811/12-TOC5

TEMPERATURE (°C)

POWER-UP RESET TIMEOUT (ms)

210

200

220

-40 85

35-15 10 60

MAX81_R/S/T

MAX81_L/M

POWER-DOWN RESET DELAY vs. TEMPERATURE

(MAX81_R/S/T)

100

MAX811/12-TOC3

TEMPERATURE (°C)

POWER-DOWN RESET DELAY (µs)

-40 85

10-15 6035

VOD = VTH - VCC

VOD = 20mV

VOD = 200mV

VOD = 125mV

RESET THRESHOLD DEVIATION

vs. TEMPERATURE

0.9995

1.0000

1.0005

MAX811/12-TOC6

TEMPERATURE (°C)

NORMALIZED THRESHOLD (V)

0.9985

0.9980

0.9990

-40 8535-15 10 60

-40 85

SUPPLY CURRENT vs. TEMPERATURE

(MAX81_R/S/T)

2.0

2.5

3.0

MAX811/12-TOC1

TEMPERATURE (°C)

SUPPLY CURRENT (µA)

1.0

0.5

-15 60

1.5

VCC = 3.6V

VCC = 3.3V

VCC = 1V

POWER-DOWN RESET DELAY vs. TEMPERATURE

(MAX81_L/M)

200

MAX811/12-TOC4

TEMPERATURE (°C)

POWER-DOWN RESET DELAY (µs)

100

150

-40 8510-15 6035

VOD = VTH - VCC

VOD = 125mV

VOD = 200mV

VOD = 20mV

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MAX811/MAX812 4-Pin μP Voltage Monitors

with Manual Reset Input

Typical Operating Characteristics

Detailed Description

Reset Output

A microprocessor’s (μP’s) reset input starts the μP in a

known state. These μP supervisory circuits assert reset

to prevent code execution errors during power-up, power-

down, or brownout conditions.

RESET is guaranteed to be a logic low for VCC > 1V.

Once VCC exceeds the reset threshold, an internal timer

keeps RESET low for the reset timeout period; after this

interval, RESET goes high.

If a brownout condition occurs (VCC dips below the reset

threshold), RESET goes low. Any time VCC goes below

the reset threshold, the internal timer resets to zero, and

RESET goes low. The internal timer starts after VCC

returns above the reset threshold, and RESET remains

low for the reset timeout period.

The manual reset input (MR) can also initiate a reset. See

the Manual Reset Input section.

The MAX812 has an active-high RESET output that is the

inverse of the MAX811’s RESET output.

Manual Reset Input

Many μP-based products require manual reset capabil-

ity, allowing the operator, a test technician, or external

logic circuitry to initiate a reset. A logic low on MR asserts

reset. Reset remains asserted while MR is low, and for

the Reset Active Timeout Period (tRP) after MR returns

high. This input has an internal 20kΩ pull-up resistor, so

it can be left open if it is not used. MR can be driven with

TTL or CMOS-logic levels, or with open-drain/collector

outputs. Connect a normally open momentary switch from

MR to GND to create a manual-reset function; external

debounce circuitry is not required. If MR is driven from

long cables or if the device is used in a noisy environment,

connecting a 0.1μF capacitor from MR to ground provides

additional noise immunity.

Reset Threshold Accuracy

The MAX811/MAX812 are ideal for systems using a 5V

±5% or 3V ±5% power supply with ICs specified for 5V

±10% or 3V ±10%, respectively. They are designed to

meet worst-case specifications over temperature. The

reset is guaranteed to assert after the power supply

falls out of regulation, but before power drops below the

minimum specified operating voltage range for the system

ICs. The thresholds are pre-trimmed and exhibit tight dis-

tribution, reducing the range over which an undesirable

reset may occur.

PIN NAME FUNCTION

MAX811 MAX812

1 1 GND Ground

2 — RESET Active-Low Reset Output. RESET remains low while VCC is below the reset threshold or while

MR is held low. RESET remains low for the Reset Active Timeout Period (tRP) after the reset

conditions are terminated.

— 2 RESET Active-High Reset Output. RESET remains high while VCC is below the reset threshold or while

MR is held low. RESET remains high for Reset Active Timeout Period (tRP) after the reset

conditions are terminated.

3 3 MR

Manual Reset Input. A logic low on MR asserts reset. Reset remains asserted as long as MR

is low and for 180ms after MR returns high. This active-low input has an internal 20kΩ pull-up

resistor. It can be driven from a TTL or CMOS-logic line, or shorted to ground with a switch.

Leave open if unused.

4 4 VCC +5V, +3.3V, or +3V Supply Voltage

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MAX811/MAX812 4-Pin μP Voltage Monitors

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Pin Description

Applications Information

Negative-Going VCC Transients

In addition to issuing a reset to the μP during power-up,

power-down, and brownout conditions, the MAX811/

MAX812 are relatively immune to short duration negative-

going VCC transients (glitches).

Figure 1 shows typical transient durations vs. reset com-

parator overdrive, for which the MAX811/MAX812 do

not generate a reset pulse. This graph was generated

using a negative-going pulse applied to VCC, starting

above the actual reset threshold and ending below it by

the magnitude indicated (reset comparator overdrive).

The graph indicates the typical maximum pulse width a

negative-going VCC transient may have without causing

a reset pulse to be issued. As the magnitude of the tran-

sient increases (goes farther below the reset threshold),

the maximum allowable pulse width decreases. Typically,

a VCC transient that goes 125mV below the reset thresh-

old and lasts 40μs or less (MAX81_L/M) or 20μs or less

(MAX81_T/S/R) will not cause a reset pulse to be issued.

A 0.1μF capacitor mounted as close as possible to VCC

provides additional transient immunity.

Ensuring a Valid RESET Output

Down to VCC = 0V

When VCC falls below 1V, the MAX811 RESET output

no longer sinks current—it becomes an open circuit.

Therefore, high-impedance CMOS-logic inputs connected

to the RESET output can drift to undetermined voltages.

This presents no problem in most applications, since most

μP and other circuitry is inoperative with VCC below 1V.

However, in applications where the RESET output must

be valid down to 0V, adding a pulldown resistor to the

RESET pin will cause any stray leakage currents to flow

to ground, holding RESET low (Figure 2). R1’s value is

not critical; 100kΩ is large enough not to load RESET and

small enough to pull RESET to ground.

A 100kΩ pull-up resistor to VCC is also recommended

for the MAX812 if RESET is required to remain valid for

VCC < 1V.

Figure 1. Maximum Transient Duration without Causing a Reset

Pulse vs. Comparator Overdrive

Figure 2. RESET Valid to VCC = Ground Circuit

1 100 1000

RESET COMPARATOR OVERDRIVE, VTH - VCC (mV)

MAXIMUM TRANSIENT DURATION (ms)

TA = +25°C

MAX81 _L/M

MAX81 _R/S/T

VCC

GND

MAX811

RESET

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MAX811/MAX812 4-Pin μP Voltage Monitors

with Manual Reset Input

Interfacing to μPs with

Bidirectional Reset Pins

μPs with bidirectional reset pins (such as the Motorola

68HC11 series) can contend with the MAX811/MAX812

reset outputs. If, for example, the MAX811 RESET output

is asserted high and the μP wants to pull it low, indeter-

minate logic levels may result. To correct such cases,

connect a 4.7kΩ resistor between the MAX811 RESET (or

MAX812 RESET) output and the μP reset I/O (Figure 3).

Buffer the reset output to other system components.

Figure 3. Interfacing to μPs with Bidirectional Reset I/O

4.7k

VCC

GND

RESET

MAX811

RESET

VCC

GND

µP

BUFFER

BUFFERED RESET

TO OTHER SYSTEM

COMPONENTS

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MAX811/MAX812 4-Pin μP Voltage Monitors

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Chip Information

TRANSISTOR COUNT: 341

PACKAGE TYPE PACKAGE CODE OUTLINE NO. LAND PATTERN NO.

4 SOT143 U4+1 21-0052 90-0183

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MAX811/MAX812 4-Pin μP Voltage Monitors

with Manual Reset Input

Package Information

For the latest package outline information and land patterns (footprints), go to www.maximintegrated.com/packages. Note that a “+”,

“#”, or “-” in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing

pertains to the package regardless of RoHS status.

REVISION

NUMBER

REVISION

DATE DESCRIPTION PAGES

CHANGED

5 6/15 Updated Benets and Features and Package Information sections 1, 8

65/18 Updated Absolute Maximum Ratings 2

Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses

are implied. Maxim Integrated reserves the right to change the circuitry and specications without notice at any time. The parametric values (min and max limits)

shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.

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MAX811/MAX812 4-Pin μP Voltage Monitors

with Manual Reset Input

Revision History

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